I must be adjusting my engines consistantly wrong. I have two engines, a Zenoah G-26, and Chinese SV-26, and both are behaving in exactly in the same way. They start easly, and run up good in the pit area. Idle to full throttle without hesitation. However, fly for 5 minutes, and then try some touch and go's, and they both spit,sputter, and die. They refuse to go from idle to full throttle.

Which needle valve do I need to turn richer, the low or the high ? Or what else should I be concerned with ?

Thanks for your help. > Ed